Former Supreme Court Justice John Paul Stevens says he thinks the federal government should legalize marijuana.

The 94-year-old retired justice tells NPR that "public opinion has changed" on the issue.

"Recognize that the distinction between marijuana and alcoholic beverages is really not much of a distinction," Steven says. "Alcohol, the prohibition against selling and dispensing alcoholic beverages has I think been generally, there's a general consensus that it was not worth the cost. And I think really in time that will be the general consensus with respect to this particular drug."

Stevens is the author of a new book, "Six Amendments: How and Why We Should Change the Constitution," in which he proposes banning capital punishment and limiting gun rights.